In a previous study, both the n. tractus diagonalis (td), a cholinergic cell body area, and the ventral tegmental area (avt), the location of the A10 dopaminergic cell bodies, showed changes in cholinergic activity in male and female rats after gonadal hormone manipulations which altered LH secretion. The neuropharmacological relationship of the td and the avt was explored in another series of experiments. Acute stimulation of the avt resulted in reduced acetylcholine concentration in the hippocampus, a well known td cholinergic projection area. In addition, both destruction of afferent catecholamine terminals in the td by 6-OHDA, and also chronic treatment with the dopamine receptor antagonist, haloperidol, caused alteration in choline acetyltransferase and acetylcholine concentration respectively, in the avt. These results suggest the presence of a feedback-type functional relationship between the td and the avt which may be pertinent to the cholinergic and dopaminergic neurotransmitter mediated effects of hormones and psychoactive drugs on behavior.